Plant genetic engineering allows plant breeders to modify the genetic makeup of a plant precisely and predictably. Both alone and in combination with traditional plant breeding techniques, genetic engineering facilitates the creation of improved varieties faster, and with greater ease, than is possible when only traditional plant-breeding techniques are available.
Isolated plant promoters are instrumental for constructing genetically engineered plants. Typically, to produce transgenic plants, an isolated plant promoter is inserted into a vector and operably linked to a heterologous DNA sequence, thereby creating an expression construct. Plant cells are then transformed with the expression construct by any of a number of art recognized methods. The result of transformation is that the plant promoter operably linked to the heterologous DNA, is inserted into the genome of the transformed plant cell, and regulation of the heterologous DNA expression in the transformed plant cell is controlled by the promoter.
There are a variety of different approaches for producing a desired phenotype in a transgenic plant. The chosen approach typically depends on the nature of the heterologous sequences coupled to the isolated plant promoter. For example, expression of a novel gene that is not normally expressed in plant, or in a particular tissue of a plant, may confer a phenotypic change. Alternatively, the expression of a sense or an antisense construct introduced into transgenic plants can cause the inhibition of expression of endogenous plant genes. This inhibition of expression can, in turn, produce a desired phenotypic change.
To facilitate the production of precise phenotypes, it is advantageous to have available a variety of different promoters for the genetic engineering of plants. Unfortunately however, promoter elements capable of directing high levels of transgene expression are difficult to isolate. Thus, such promoters remain limited in number, and as a result, there is a continuing demand for new promoters.
An exemplary plant promoter used for plant genetic engineering is the CaMV 35S promoter. Derived from the cauliflower mosaic virus, the CaMV35S promoter is the promoter of choice for much of plant genetic engineering. Indeed, it is used in almost all genetically modified crops currently grown or tested.
The CaMV 35S promoter is a strong, constitutive promoter which delivers high expression of operably linked genes in almost any type of cell or tissue of a plant, at any developmental stage. But, despite its current popularity, a number of problems associated with use of the CaMV 35S promoter make its use less than ideal. For example, in addition to being protected by patents that limit its use in the commercial sector, use of the CaMV promoter has provoked concerns about the safety of a promoter that is derived from a virus.
Indeed, some consumers, along with a few advocacy groups, have voiced concern about the safety and environmental impact of genetically engineered food products. Typically, concerns about food safety center around the breaking and joining up of otherwise incompatible genetic material, thereby increasing the chances for horizontal transmission to unrelated species. (see e.g., Nowora, T. et al (1999). Virology 255, 214-20, Maiss, E., et al (1992). J. Gen. Virol. 73, 709-13; Meyer, M and Dessens, J. (1997). J. Gen. Viol. 78, 147-51).
Genetic engineering offers tremendous potential for the production of better and more plentiful products. However, genetic engineering is still a fledgling economic force in the commercial food business and so is far from reaching its full potential. Ultimately, the success or failure of genetically engineered foods depends not only on the quality or quantity of what genetically engineered plants can produce, but instead on public acceptance of the products. Therefore, producers of genetically engineered crops need to ensure that the public is comfortable with the safety of their products.
Thus, what is needed in the art, are genetically engineered foods that are readily accepted by the public. To meet the demand for safe acceptable produce, what is needed are promoters that are publicly acceptable and do not provoke safety concerns, and which at the same time, are effective at controlling gene expression and producing desired phenotypes. Such promoters should be capable of directing high levels of transgene expression, should be useful in many different applications, and should be plant derived. Such promoters would avoid or eliminate many if not all of the drawbacks associated with the most popular promoters e.g., CaMV 35S promoter, and thus would facilitate the acceptance of genetically engineered products.
Fortunately, as will be clear from the following disclosure, the present invention provides for these and other needs.